Coaxial switch



Dec. 10, 1957 D. B. CHERRY 2,816,198 COAXIAL swz'rcn Filed Nov. 5, 1954 32. an I 068/7 6'. Cherry km, 29.; zqfi 7'5.

Dean B. Cherry, Cleveland, Ohio, assignor toThompson Products, Inc., Cleveland, l1i0, a corporation of Ohio I Application November-5, 1954, SrialNc. 467,170 r 5 Claims. (c1. zooise This invention relates to improvements in coaxial switches, i

In one type of coaxial switch now in commercial use, the coaxial lines to be interconnected are secured to terminals of a switch housing having a central rotor chamber. The inner and outer conductors of each terminal are disposed for continuity with the inner and outer conductors of a switch rotor within the chamber. Continuity between the. outer conductors of the terminals and the rotor outer conductor is based on axial alignment of the conductors with a su-fiicient peripheral clearance or gap to allowrotation of therotor in the housing.

The present invention is particularly concerned with such a coaxial switch, and is based on the discovery that cross talk between the interconnected terminals and the remaining non-connected terminals of the switch can be substantially reduced by positively grounding the rotor to the switch housing across the peripheral-gap therebetween as close as possible to the-R.-.F. channel being used and/or providing electrostatic shielding at the pe ripheral gap as close as possible to the R.-F. channel being used. For example, for aswitch having a positive ground between the rotor and housing at the gap as illustrated in the accompanying drawings, a minimum reduction in cross talk of 15 'db and an average reduction of 25 db at 3000 megacycles were obtained. Thus, while without the positive ground at the .gap the switch could only meet a 50 db cross talk specification, with the positive ground of the present invention the same switch was able to meet a minimum cross talk specificat7ion of 65 db and an average cross talk requirement of 5 db.

It is therefore an important object of the presentinvention to provide a novel and improved coaxial switch structure.

Another object of 'the invention is to providea coaxial switch having a reduced cross talk characteristic.

Still another object of the invention is to provide a coaxial switch which readily adapts itself to large scale production methods and which .is readily assembled.

A still further object of the present invention is to provide a particularly economical and simple means for materially reducing cross talk in coaxial switches.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description taken in conjunction with the :accompanying drawings, in which;

Figure 1 is a partial longitudinal sectional View of a coaxial switch having a cross talk reduction means according to the present invention applied thereto;

Figure 2 is a fragmentary transverse sectional view taken through :the coaxial switch of Figure 1 just below the upper flange of the switch rotor to show the cross talk reduction means in relation to the body of the rotor; H

Figure 3 is a plan viewof a cross talkreduction means constructed in accordance with the present invention; n

2,816,198 Patented Dec. 10, 1957 vides a central axial terminal 11 for receiving a: coaxial line to be interconnected with either a first branch line connected with terminal 12 or second branch line connected with terminal 13 of the housing. The terminals are illustrated as externally threadedfor connection with the coaxial lines and have internal cylindrical passages 15, '16 and 17, respectively, leading to central rotor chamber 18.

The terminals have coaxial therewith inner conductor members 21, 22 and :23 for electrical continuity with the inner conductors of the respective lines connected with the terminals. These inner conductors are supported within the passages by means of. dielectric sleeves 26, 21 and 28 which are retained in the passages against axial displacement by metal insert members 30, 31 and 32 at the outer ends and by internal shoulders 34, 35 and 36 at their inner ends.

Disposed in the chamber 18 for establishing selective continuity between the central terminal 11 and branch terminals 12 and 13 is a rotor member 40. This rotor member has upper and lower cylindrical flanges 41 and 42 of diameter to fit closely within the cylindrical rotor chamber 18. Between these flanges extends a 'seg'fn enta'l rotor body 45 (Figure 2) having a semi-cylindrical exterior wall portion 50 merging into parallel sidewall portions 51 and 52 which in turn are joined 'by a segmental cylindrical face '53 on the 'outerfper iphery of the rotor and flush with the exterior periphery of the fiangcs 4'1 and 42. v

For defining an outer conductor to bridge between the outer conductor of terminal 11 and the outer conductors of terminals 12 and 13, the rotor 40 is provided with a curved rotor passage 56 extendingfrom the central portion of the upper surface of the rotor in coaxial alignment with the passage 15 of terminal 11 downwardly and radially outwardly of the rotor to terminate centrally of the peripheral face 53 "of the rotor. Disposed in this "rotor passage 56 is a rotor elbow conductor 58 mounted by means of dielectric sleeve 59. The ends'SSa and 58b of the elbow conductor 58 terminate generally flush with the top surface of the rotor and with the peripheral face 53, respectively. The sleeve 59 is counterboredat the top asindic'ated 'at61. I

For retaining the rotor sleeve 59 in "place during machining operations, a hole is drilled longitudinally 'through the rotor as indicated at "64 jwhichinterscts the ductor 21 of the fitting 11 and the inner conductor 23 of the fitting 13, the walls of the rotor will be spaced from the inner conductor 22 to preventshort .circniting of the inner conductor 22 to its associated outer conductor provided by the passage :16. This feature disclosed and claimed in Jacques and Gates application, Serial No. 294,788, assigned to the same ass'ignee as the present invention.

For moving the "rotor between switching positions, the rotor is provided with an integral shaft 70 depending therefrom. The rotor shaft 70 extends axially through an aperture in a mounting plate 72. An inner boss 75 on the mounting plate 72 carries a bearing collar 76 which slidably receives the rotor shaft 70 therethrough. A spring" washer 81 is interposed between the collar 76 and the lower surface of the rotor flange 41 and the switch isfs ode'signed' the spring washer is placed under compression in assembled relation to urge'therotor upwardly in the chamber 18.' On the lower sideiof the plate 72, a ratchet wheel 83 is securedto the shaft 70, the ratchet"whee1 cooperating with detent means to establish precise switching positions of the rotor, for example in'the manner described'in Schunemann and Thoren application, Serial No., '267,246 assigned to the same assignee as thein stant application.

It will be understood that the rotor may be moved between switching positions by a suitable indexing mechanism such as disclosed in Elliottapplication, Serial No. 259,979 assigned to the same assignee as the present application, the housing for said indexing mechanism being attached to'the mounting plate 72.

The side conductors 22 and 23 preferably comprise stationary fixed members which terminate substantially flush with the side wall of the chamber 18 to extend a close relation to the end of 58b of the rotor conductor 58 when registered therewith. However the conductor 21 has a cylindrically bored recess extending axially thereinto from the lower end whichreceives a spring 90 andplunger 91 therein. The plunger acts on the elbow conductor 58 to urge the elbow conductor-insulating sleeve unit arcuately downwardly in the elbow passage 56 to press the radial end 58b of the elbow conductor .58 against the stationary inner conductor 23.

The lower end of inner conductor 21 is slotted from its lower margin to provide vertically elongated fingers 21a surrounding'plunger91 and having lower free ends. The fingers 21a are crimped inwardly so as to estabh'shpo'sitive engagement between the plunger 91 and illustrated embodiment maybe .780 plus .or minus.-001

inch. The spacing between the side walls 51 and 52 of the segmental rotor body portion 45 may be .500 inch.

In initial condition of the shim with legs 109 and 110 parallel, the legs 109 and 110 may 'be separated by distance of .453 inch, and the legs may be .640 inch long. After bending the shim to the configuration of Figure 3, the distance end to end is reduced to .620 inch, while the maximum bowing measured from point 102 to the most remote lateral point of the leg "109 may be .047 inch. The bowed legs,10 9 and 110 area maximum of .620

- plus or minus .030 inch apart with a .495 block in the open end between points 102 and 103. The shim may be made of stainless steel and be .005 inch thick and .437 plus or minus .015 inch high. The rear end face 112 of the shim should be parallel to its forward rounded faces 113 and 114 to within very close tolerances. The distance between the flanges 41 and 42 of the rotor may be .519 inch for example.

As illustrated in Figure 3 the rounded faces 113 and 114 are defined by turning the ends 115 and 116 of the shim inwardly, the faces'being in wedged engagement between the sides 51 and 52 of the rotor and the cylindrical wall of the rotor chamber 18. Additional con tact with the wall of the rotor chamber is made at points 104; and"1 05. It will 'be understood that the shim is so dimensioned as to be under a resilient compression when in assembly with vthe rotor within the rotor chamber;

' It will 'be" understood that many modifications and variations may be effected without departing from the the.fingers. By this means, R.-F. energy is shunted past I spring 90 to prevent'the spring from acting as an inductance; at highffrequencies. v

J The pressure exerted by fingers 21a on the plunger is preferably adjusted so that the plunger will not drop out of tlie'housing whenthe housingis given a sharp rap on the palm of thehand before assembly of the rotor; and so that after depressing the plunger into the inner con- 'ductor recess and slowly releasing, the plunger extends aminimuin'of .035 inch above the adjacent wall of the rotor chamber with the housing inverted.

As illustrated'in Figures 1 and 2, resilient conducting means is interposed between the rotor and the side wall of the rotor chamber. It has been found that by this provision, the cross talk of the switch is very materially reduced as discussed heretofore. Specifically, in the "illustrated embodiment, the resilient conducting means comprises a stainless steel shim 100 which is clipped around the segmental rotor body portion 45. As illustrated in Figure 2, the shim 100 provides elongated conduo-tive portions 113 and 114 in resilient wedged engagementwiththewall of the rotor chamber and with the wall of the-rotor and bridging the-peripheral clearance gap therebetween closely adjacentto the R.:F. channel of the housing: registered'therewith as shown in Figure 1. Theshim .100 thus provides. a positive conductive connection or ground between the rotor and housing .across the peripheral gap therebetween as well as providing electrostatic shielding at the gap.

The shim 100maybe so dimensioned that with a .495

.plus or-minus .001 inch block between the legs of the shim at point 102 and point 103, points 102, 103, 104

and 105 will contact a circumscribed circle of .788 plus -.-in use as defined by the rotor. outer conductor passage 17 v or minus .OOI inchdiameter but will not contact with scope of thenovel concepts of the present invention.

I claim as 'my invention:

'1. In a rot'ary' switch construction, a housing having a generally cylindrical rotor chamber, a rotor rotatably mounted in said chamber and having generally axially extending wall portions spaced from the side wall of said chamber, and a flat spring member of substantial axial extent confined between the walls of the chamber and the walls of said rotor under resilient compression.

2. 'A rotary coaxial switch construction comprising a housing having a plurality of peripherally spaced switching stations therein,'a rotor movably mounted in said chamber and having a rotor inner conductor for switching continuity with the respective stations, the rotor including a segmental body portion having a semi-cylindrical exterior wall portion and generally parallel wall portions extending from the opposite margins of said semi-cylindrical (wall portion to the periphery of the rotor, and a crosstalk shim of thin flat construction embracing said segmental rotor body portion and of generally U-shape with corners of the base leg thereof engaging. against the wall of the chamber and with the ends of the side leg portions wedged against the side walls of the rotor body portion. v

3. A rotary coaxial switch construction comprising a housing having a chamber with a plurality of peripherally spaced switching stations therein, a rotor movably mounted in said chamber and having an inner conductor for switching continuity with the respective stations, the rotor inexterior end wall portion and generally parallel side wall portions extending from the opposite margins of said semicylindricalend wall portion to the periphery of the rotor, and' a crosstalk shim of thin fiat construction embracing said segmental rotor body portion and of generally U- shape with corners of the base leg thereof engaging against the wall of the chamber and with the ends of the side leg portions wedged between the side walls of the rotor body portion and the adjacent portions of the wall of the chamber. 4

4'.'--A high frequency switch construction, comprising a switch body, a switch member angula'rly movable relative to the switch body with a peripheralclearancegap therebetween, said switch member in one angular position thereof providing a high frequency channel extending in said switch body and in said switch member and across said clearance gap therebetween, and cross talk reducing conducting means positioned closely adjacent said channel 5 at said gap.

5. A high frequency switch construction comprising a switch body, a switch member angularly movable relative to the switch body with a peripheral clearance gap therebetween, said switch member in one angular position 10 thereof providing a high frequency channel extending in said switch body and in said switch member and across said clearance gap therebetween, and cross talk reducing conducting means positioned closely adjacent said channel at said gap and positively engaging said switch body and said switch member and bridging therebetween at said gap.

References Cited in the file of this patent UNITED STATES PATENTS 2,556,869 Charles June 12, 1951 

